1. Field of the Invention
The present invention relates to systems and methods for mounting electrical equipment at an electrical substation.
2. Prior Art
An electrical substation is a part of an electrical generation, transmission, and distribution system. Substations transform voltage from one voltage level to another, or perform any of several other important functions. Between the generating station and consumer, electric power may flow through multiple types of substations with different functions operating at different voltage levels.
Electrical substations are expensive and time-consuming to deploy. An electrical substation may cost $60 million and take more than 5 years to deploy. The permit approval process may require multiple ecological and safety studies which slow down the overall deployment. An electrical substation usually contains multiple, heavy current and voltage-controlling devices such as transformers, capacitors, switches, etc. Electrical substations employ many different methods for mounting these current-controlling devices. Electrical substations are usually designed for a specific, permanent deployment and cannot easily be disassembled and re-deployed at a second location.
The current and voltage-controlling devices need to be mounted so they are easy to install and maintain. Each device has specific mounting requirements which include: operating voltage levels, orientation, device spacing and visibility or signal path. Each deployment of the support structure requires a full understanding of the local environmental, seismic and geotechnical conditions. The design of the mounting structure depends on the loads it will experience and the local geotechnical conditions. The soils ability to resist the load often has the greatest effect on the structural solution and selection.
Using the normal, industry-standard, structural-design practice, each support is designed to meet the unique conditions for the location it will be deployed in. This approach results in structural members, foundation mounting and anchoring conditions that are unique to each location and which cannot be disassembled and redeployed in another location without significant construction and reconfiguration costs. Most of the currently available designs either have a strong dependency on the local soil conditions requiring substantial customization or are structurally inefficient needing expensive and time consuming construction methods.
FIG. 1 (Prior Art, U.S. Pat. No. 6,215,653) shows a modular substation design that is easy to erect and disassemble. The transformer 23 is mounted on a central section of base 2 and flanked by structures 4 and 5. The design requires the base of the structure to be tied to all structural elements. In situation where numerous electrical devices need to be installed, the base restricts maintenance access. The beams needed to tie the columns together require steel members that are fairly high, e.g., ˜12″ or more. The beams become physical access barriers for maintenance equipment. Maintenance equipment cannot and should not drive over those structural members after they have been installed.
The maintenance requirement can be met by vertically mounting the electrical devices at an elevation. FIG. 2 (Prior Art, U.S. Pat. No. 3,556,310) shows vertical mounting of the electrical devices 13. However in medium-voltage (MV) and high-voltage (HV) applications, the electrical devices have horizontal spacing requirements that prevent close coupling of the device 13 and the structural members 12. While FIG. 5 (Prior Art, U.S. Pat. No. 4,277,639) addresses the use of electrical devices at elevation with the horizontal spacing requirement, it also supports each device with its own independent support. Transformer 1 is supported by insulators 14 and 16; and transformer 2 is supported by insulator 24 and 26. This method leads to a structurally inefficient design when used in a configuration that requires multiple electrical devices. Each structure supports the device and resists the loads independently.
FIG. 3 (Prior Art, U.S. Pat. No. 4,710,850) and FIG. 4 (Prior Art, U.S. Pat. No. 4,577,826) show a completely different approach. Both provide electrical isolation in HV and MV applications through the use of an insulated, elevated substation. These implementations require the use of structural insulators as the primary force resisting elements. In FIG. 3 stories 2, 4, 6, 8, 10 and 12 are connected to each other by outdoor-type insulators 27 which are connected to the node elements 24. In FIG. 4, platform 4 is supported by insulator columns 6. These structural insulators are expensive to use and are designed to meet the specific requirements of the application and location. Using the same structural insulators in a different application requires substantial redesign and cost.
Mounting MV and HV electrical devices at elevations provides safe access to the devices for installation, replacement and maintenance. The electrical device spacing clearance distances depend on the voltage levels. The spacing clearance provides electrical insulation and reduces mutual thermal radiation effects. The clearance and spacing requirements of electrical devices lead to tall structures with large foot prints. The larger structures result in longer spans and higher elevations requiring heavier and stronger structural members to resist the forces. The larger members result in higher fabrication and construction costs. Additionally, the larger footprints lead to secondary problems regarding land availability, acquisition, zoning constraints and permit requirements.
Currently mounting MV and HV devices on elevated structures is limited as in FIG. 5 (Prior Art, U.S. Pat. No. 4,277,639). FIG. 5 shows an electrical device centrally mounted on a structure and supported by insulators to achieve the elevation and clearance requirements. The electrical conductors are mounted horizontally and to the mid body of the device. The vertical, wind and earthquake loads on the transformer devices 1 and 2 are transferred to the A-frame structure through the use of insulators, 12, 16, 24 and 26. In order to install numerous devices a minimum amount of clearance is required radially from the conductors 4 and 5 to other conductors, structural components or devices on a different phase. While this option is viable for a small number of device deployments, it leads to accessibility and enlarged foot print issues when numerous devices need to be deployed in series or parallel.
There is a need for an electrical substation support structure that solves the described issues.